1. Field of the Invention
The present invention relates to display fabrication, and more particularly to an improved method for aligning lenticular sheets with active pitch control for display devices.
2. Description of the Related Art
Displays, such as, liquid crystal displays, have found a wide range of uses in modern electronic equipment. With the improvement of viewing quality and the reduction of viewing angle limitations, liquid crystal displays have become more appealing for a plurality of new applications and well as more desirable for old applications. Different effects are sometimes desirable for these display screens. One effect may be realized by the inclusion of a lenticular sheet.
Lenticular arrays or sheets may be employed on a display screen or on a photograph to give the appearance of depth to the image displayed. The lenticular sheet or array focuses light in a desired way to provide improved viewing angle or to cause the eye of a viewer to see different elements of the overall image. Lenticular sheets typically include a plurality of parallel convex lines which function as lens"" for directing light from an underlying pixel or image.
In many instances, especially for display screens, it is necessary to align a lenticular sheet with underlying components. In the case of displays, it is desirable to align the lenticular sheet relative to a black matrix layer patterned on glass. The black matrix functions as a barrier to any undesirable light transmission or reflections occurring in the vicinity of light transmitting components, such as pixel electrodes. Alignment of the lenticular sheet needs to be consistent with the underlying components with an accuracy of, for example, a few microns across the entire width of a display which can be 28 cm or more wide.
It is very difficult to fabricate the lenticular sheet with the needed accuracy since any pitch error can result in a large cumulative pitch error when there are, for example, a thousand or more lenticular lines needed for each display. Further, problems arise when shifts in the lenticular sheet occur or temperature variations occur during processing.
For the pitch error to be less than 20 microns, for example, the individual lenticular pitch should have a systematic variation of less than 0.02 microns. This is compounded by the need for very precise temperature control due to large thermal coefficients of expansion of plastics used for lenticular sheets.
Therefore, a need exists for a method for aligning lenticular sheets which accounts for process and temperature variations. A further need exits for a method for accurately aligning lenticular sheets with active control.
A method for aligning a lenticular sheet, in accordance with the present invention, includes applying curable, preferably transparent, adhesive to a surface and placing a lenticular sheet over the curable adhesive on the surface. The adhesive is cured at a first end portion of the lenticular sheet such that the first end portion is aligned with a first reference position. A temperature of the lenticular sheet is adjusted to align a second end portion of the lenticular sheet with a second reference position. Remaining portions of adhesive are cured to secure the lenticular sheet.
In other methods, the curable adhesive is preferably cured by applying radiation. The surface may include a polarizer for a display device. The surface may includes a color filter for a display device. The first reference position may include one of a pixel and a feature of a black matrix layer. The second reference position may include one of a pixel and a feature of a black matrix layer. The step of adjusting a temperature of the lenticular sheet may include the step of heating the surface to expand the lenticular sheet. The step of adjusting a temperature of the lenticular sheet may include the step of cooling the surface to contract the lenticular sheet. The step of adjusting a temperature of the lenticular sheet may include step of heating the lenticular sheet with an infrared heater. The first end portion may be aligned with a first reference position by employing alignment marks. The second end portion may be aligned with a second reference position by employing alignment marks. The step of adjusting a temperature of the lenticular sheet may include the steps of modifying the temperature of the lenticular sheet, observing a change in position of the lenticular sheet with respect to the second reference position, and readjusting the temperature to provide alignment between the lenticular sheet and the second reference position.
Another method for aligning a lenticular sheet, in accordance with the present invention includes the steps of providing a lenticular sheet having a plurality of lenticulars, applying a curable adhesive on a surface of a display device, the display device including a plurality of pixels, placing the lenticular sheet over the curable adhesive, aligning a first lenticular of the lenticular sheet with a first pixel position, curing the adhesive at the first pixel position to secure the lenticular sheet at the first pixel position, adjusting a temperature of the lenticular sheet to align a second lenticular of the lenticular sheet with a second pixel position wherein the first and second pixel portions are set apart from one another, and curing remaining portions of adhesive to secure the lenticular sheet such that alignment between the plurality of pixels and the plurality of lenticulars is achieved between the first and second pixel positions.
In other methods, the curable adhesive is preferably cured by applying ultra violet radiation. The surface may include a polarizer for the display device. The step of adjusting a temperature of the lenticular sheet may include the step of heating the surface to expand the lenticular sheet, or cooling the surface to contract the lenticular sheet. The step of adjusting a temperature of the lenticular sheet may include the steps of modifying the temperature of the lenticular sheet, observing a change in position of the lenticular sheet with respect to the second pixel position, and readjusting the temperature to provide alignment between the lenticular sheet and the second pixel position.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.